4 ms·

> Yes, that is exactly what I'm saying. Sorry to be a stickler for detail, but earlier you defined "faithful" to mean the future is a function of the present,

by kmill 9y ago

> Yes, that is exactly what I'm saying. Sorry to be a stickler for detail, but earlier you defined "faithful" to mean the future is a function of the present, and now you're saying that "the past and future are functions of the present" is exactly what you are saying. Perhaps you mean that it's exactly what you intended to say? I'm not intending to undermine anything with "gotchas." It just seems to me that more precision will help your arguments. One thing I do not see, in your essay, is how reducing "memory" to "entanglement" means time is asymmetric. What is it about entanglement that is asymmetric that isn't just "that's how entanglement is defined"? I also do not understand how the thought experiment implies time travel cannot happen. Has anyone proved that the wave equation has no solutions when there are closed timelike curves? (I assume not since there are papers studying quantum computations possible in the presence of closed timelike curves, for instance.)

lisper 9y ago
All of those statements are consistent with the concept that I am attempting to communicate through the imprecise medium of natural language. > What is it about entanglement that is asymmetric that isn't just "that's how entanglement is defined"? Entanglement is symmetric. You can reverse an entanglement. But only by returning the entangled particles to the same physical location. The reason that this symmetric quantum process gives rise to (what appears to us to be) a time-asymmetric classical universe is that what we classical entities actually are is massively entangled systems of vast numbers of quantum particles (or, to be as precise as I can, we are quantum systems with a vast number of mutually entangled degrees of freedom). All those entanglements can be reversed, but if you reverse them, the result is not "moving backwards in time" as humans commonly conceptualize it. The result is rewinding the whole universe to a previous state. That is actually possible in principle. As I note at the end of the essay, there is no way to distinguish a universe that is constantly being rewound and replayed from the universe we live in. But what most people think of as going backwards in time is rewinding the whole universe with the exception of themselves to a previous state. That's not possible. I don't actually know what the consequences are of applying this idea to CTCs. I don't understand CTCs well enough to do it myself. There's probably a thesis or two in there somewhere. Mixing QM and GR is a rare skill.

by kmill 9y ago

lisper 9y ago

All of those statements are consistent with the concept that I am attempting to communicate through the imprecise medium of natural language. > What is it about entanglement that is asymmetric that isn't just "that's how entanglement is defined"? Entanglement is symmetric. You can reverse an entanglement. But only by returning the entangled particles to the same physical location. The reason that this symmetric quantum process gives rise to (what appears to us to be) a time-asymmetric classical universe is that what we classical entities actually are is massively entangled systems of vast numbers of quantum particles (or, to be as precise as I can, we are quantum systems with a vast number of mutually entangled degrees of freedom). All those entanglements can be reversed, but if you reverse them, the result is not "moving backwards in time" as humans commonly conceptualize it. The result is rewinding the whole universe to a previous state. That is actually possible in principle. As I note at the end of the essay, there is no way to distinguish a universe that is constantly being rewound and replayed from the universe we live in. But what most people think of as going backwards in time is rewinding the whole universe with the exception of themselves to a previous state. That's not possible. I don't actually know what the consequences are of applying this idea to CTCs. I don't understand CTCs well enough to do it myself. There's probably a thesis or two in there somewhere. Mixing QM and GR is a rare skill.